Cob with living roof

[Renewables at aol.com]

Rob Roy uses W. R. Grace's Bituthene waterproofing membrane, which is now
called System 4000. It is a top surface of two layers of cross-laminated black
polyethylene over a 60-mil (1/16 inch) base of sticky rubberized asphalt. The
rolls are three feet wide by 35 feet long, so they cover about 100 square
feet. It is used in conjunction with a thin coating of a compatible primer if
putting it onto a wooden deck.

Rob has used this product on his earth roof since 1980 with great results. He
usually put 4" (two layers of two inch laid cross wise) of rigid insulation, a
layer of HEAVY plastic, two inches of #2 stone, and then 6" - 8" of sods. The
roof drains to the edges of course depending on called out design. The
Bituthene overlaps the drip edge flashing slightly. Instead of using heavy
timbers to retain the earth, Rob uses mossy sods that nit together.

Rarely does his roof drain much water as it absorbs almost all of the rains
(his structures are overbuilt for lots of snow and rain). He has never had to
water the wild flowers on his roof and the evaporation action helps to keep
the roof cool during the summer. A 2 - 3 foot thick snow build up adds greatly
to the roof insulation to keep the place warm in the winter.

I recommend you consult his many books to get the exact details. I think his
designs work very well with cob.

Dave

In a message dated 11/2/98 10:40:44 AM Central Standard Time,
Otherfish at aol.com writes:

<< question:
 what is your waterproof membrane?
 we are going to put a 6" sod/living roof on the berkeley cob tool shed
project
 & plan on using a torchdown modified bitumen membrane over the wood roof
 sheathing
 -we have yet to select a specific manufacturer / brand
 -can you comment?
 
 -or has anybody on the list dealt with a torchdown product or some other
 membrane for this & what did you use?
 
 thanks
 &
 cob on
 john fordice
 TCCP
 otherfish at aol.c >>